1. Field of the Invention
The present invention relates to a pulse wave analysis apparatus and a pulse wave analysis program product and, in particular, to a pulse wave analysis apparatus and a pulse wave analysis program product for automatically extracting characteristic points of a pulse wave.
2. Description of the Background Art
Blood pressure is the pressure exerted against the internal walls of the arteries by blood flow generated by contraction and expansion of the heart, and consists of systolic pressure that is the blood pressure in a systolic phase of the heart and diastolic pressure that is the blood pressure in a diastolic phase of the heart. Pressure pulse wave of the intra-arterial pressure is a composite wave of an early systolic component (ejected wave) generated by ejection of blood from the heart and a late systolic component (reflected wave) generated by reflection mainly from the arteries.
Japanese Patent Laying-Open No. 07-039530 discloses an automatic sphygmomanometer that automatically analyzes the early systolic component and the late systolic component by determining a fourth derivative wave of the original waveform of a pulse wave.
The conventional automatic sphygmomanometer as disclosed in Japanese Patent Laying-Open No. 07-039530 uses a zero crossing point of the fourth derivative wave to determine the early systolic component and the late systolic component.
The zero crossing point used for determining the early systolic component and the late systolic component, however, is indefinite in some cases.